Spinal surgery is a common medical procedure in the United States and throughout the world. Spinal surgery is typically performed to decompress nerves and/or to stabilize the spinal elements. Spinal surgery can involve either anterior or posterior approaches to the spine. There are variations in the spinal anatomy of the cervical, thoracic, and lumbar levels of the spine. However, there are common anatomical elements of the spine at all the levels. The anterior bone elements of the spine include the vertebral bodies, with the interposed intervertebral discs. The posterior bone elements of the spine include the lamina, the spinous processes, the facet joints, the pedicles, and the transverse processes. Several ligaments, including the anterior longitudinal ligament, the posterior longitudinal ligament, the ligamentum flavum (or interlaminar ligament) and the interspinous ligament provide fibrous connections between the bone elements and contribute to the mechanical stability of the spine.
The spinous process of a vertebra is directed backward and downward from the junction of the laminae, and serves for the attachment of muscles and ligaments. The spinous process may be described as the protrusion on the center of the back of a vertebral body. The spinous process is the bone that can be felt down one's back. The paired transverse processes are oriented 90 degrees to the spinous process and provide attachment for back muscles.
Spondylolisthesis is a condition in which a bone (vertebra) in the lower part of the spine slips out of the proper position onto the bone below it, such as an anterior slip of a vertebrae in relation to the vertebrae immediately below it. In degenerative spondylolisthesis, the forward translation of the vertebral body may also cause narrowing of the central spinal canal at the level of the slip. The narrowing of the canal in degenerative spondylolisthesis has been referred to as the “napkin ring effect.” An illustrative description as one imagines the spinal canal as a series of napkin rings with one of the rings slid forward in comparison to the others. Subluxation of the upper adjacent vertebrae to the one below it may cause degenerative spondylolisthesis. The levels generally involved in the pathology include 90% at L4-L5, and 8% at L3-L4 and 2% at L5-S1. The degree of subluxation is less than 50% (grade 1 to 2) without surgery.
Degenerative spondylolisthesis may occur in older patients over forty years of age, and in more prevalent in patients over the age of sixty. Aging degenerative may show changes in the interverebral disc of the two vertebra adjacent to each other and the posterior articular process of the facet joints. Degenerative spondylolisthesis also is more common in females than males, and degenerative spondylolisthesis is more common in diabetes patients.
The translation of one vertebra and the other may present with symptoms of stenosis. The disc protrudes posteriorly into the vertebral canal. This may be referred to as a pseudo-herniated disc because of the slip. Degenerative spondylolisthesis may present with symptoms of neurologic claudication with lumbar spine pain, thigh pain, cramping from prolonged standing or walking. Treatments may include bracing, anti-inflammatory steroids, and physical therapy. Surgery including surgical fusion also may be employed to stabilize the segment and decompress the spine. There is a need for a cost-effective treatment that avoids the contraindications of other treatments.